The present invention relates to methods and apparatus for pumping gases out from a vacuum process chamber such as entrance loadlock, exit loadlock, transfer chamber, reaction chamber, and any other vacuum module where the wafers are processed in manufacturing semiconductor electronic components.
In manufacturing semiconductor electronic components, an important step consists in treating a semiconductor substrate in a controlled atmosphere at very low pressure, e.g. for depositing layers of various materials by plasma deposition.
In industrial production, substrates, in the form of wafers, are conditioned and brought successively into a process chamber through an airlock or through a transfer chamber. In the vacuum chambers, the atmosphere must be controlled very accurately, in particular to avoid the presence of any impurity or of any pollution.
Progress made in recent years in the semiconductor industry is essentially related to the increase in the integration of electronic circuits into components of a few square millimeters in area, defined on silicon wafers that are increasingly large.
Numerous (up to 400) technological steps are required to make such circuits, and, during the process, the pressure in the process chamber is subjected to sudden variations between various steps during which the pressure must be controlled and set to appropriate values.
Generating the low-pressure controlled-atmosphere in the chamber requires the use of effective pumping systems, generally comprising a primary pump whose outlet is connected to atmosphere and whose inlet is connected to the outlet of a secondary pump such as a turbomolecular pump whose inlet is connected to the chamber.
The process steps in the process chamber require the presence of special gases, and, by acting on the substrate, they generate gaseous compounds that must be removed. As a result, the pumping system must pump a variable atmosphere containing gaseous compounds that must be treated by gas treatment apparatus in order to deliver to atmosphere only compounds that are inoffensive.
Currently, pumping and gas treatment systems are situated remote from chambers, i.e. they are connected to chambers via long and costly pipes that are over ten meters long.
The reason behind that distance and those pipes is that current pumping and gas treatment systems are heavy and voluminous, and they give rise to adverse effects such as vibrations that it is essential to avoid in the process chamber.
Currently, an electronic component factory is therefore designed in a building having at least two levels, the upper level containing the process chamber(s), and the lower level containing the pumping and gas treatment apparatus. Pipes interconnect the two levels to convey the vacuum.
The pipes which are essential in known structures suffer from several drawbacks:
the pipes themselves generate vibrations;
the pipes constitute a large surface area on which the pumped gases can deposit in the form of particles; particles deposited in that way can backscatter from the pipe into the vacuum chamber, thereby increasing the contamination of the chamber during subsequent steps of the process;
the pipes require major mechanical support means;
to reduce the deposits in the pipes, it is possible to provide temperature control, but such control is extremely costly and very difficult to implement;
a monitoring and control system that is complex to implement must be provided for reasons of safety in the event of leakage, since the pumped gases are harmful;
the considerable amount of space needed requires large facilities and large floor areas for the factories; their cost is very high; losses from the cold line are non-negligible.
An object of the invention is to integrate in the immediate vicinity of the vacuum chamber the various elements making up the vacuum line, thereby eliminating the problems due to the piping. An object is thus to design a system that can be connected directly to the vacuum chamber, thereby making it possible to direct the effluent as quickly as possible to the gas treatment apparatus, thereby improving the effectiveness thereof.
But a problem is then that the immediate proximity of the active members of the vacuum line constitutes an increased risk of polluting the vacuum chamber, it being possible for the pollution to be, in particular, chemical, thermal, or mechanical.
For this reason, the invention aims both to reduce the cost of the installations by avoiding the presence of pipes between the process chamber and the pumping and gas treatment apparatus, and also to reduce the risks of polluting the vacuum chamber.
Another object of the invention is to facilitate adapting the pumping system to various vacuum chamber structures, by optimizing the effectiveness of the process control in the vacuum chamber.
Another object of the invention is to improve the effectiveness of the gas treatment in order to eradicate or to reduce appropriately any discharge to the atmosphere of toxic matter.
A problem resulting from the immediate proximity of the active members of the vacuum line relative to the process chamber is that the active members risk occupying a significant amount of room around the process chamber, thus preventing users from circulating around the process chamber, and also preventing other appliances that might be necessary from being put into place.
Another object of the invention is thus to leave the circulation space around the process chambers free, by preventing the active members of the vacuum line from occupying said circulation space.
Another object of the invention is to make it possible to dispose the pumping means in the immediate vicinity of the process chamber, in particular by reducing the size of said means.
To achieve these objects and others, the invention provides apparatus for conditioning the atmosphere in a vacuum chamber, said apparatus comprising:
a pumping line comprising a primary pump and at least one upstream secondary pump;
downstream from the primary pump, gas treatment means for treating the extracted gases;
wherein
the vacuum chamber is contained in a room having a false floor covering a space;
the primary pump is housed in the available space under the false floor, in the proximity of the vacuum chamber.
The gas treatment means may advantageously be housed in the available space under the false floor.
In a first alternative, the false floor comprises removable floor tiles covering the primary pump, the gas treatment means, and the gas analyzer means.
In a second alternative, the top portion of the primary pump and the top portion of the gas treatment means themselves constitute surface portions of the false floor.
A support plate can advantageously be disposed in the floor beneath the primary pump and the gas treatment means.
In an advantageous embodiment, making it possible for the operation of the process chamber to be further improved, the primary pump and the gas treatment means are enclosed together in an isolation enclosure.